Nonimpact recording apparatuses have been getting attention in business and other environments because their operation noise is small. Among them, inkjet recording apparatuses have recently come in widespread use, because they can record at a high speed on plain paper without the need for special fixing processing. In particular, on-demand-type inkjet recording apparatuses, among others, have been becoming increasingly widely used in recent years, because of low operation noise, high-resolution image output, and other characteristics.
Since recording heads used in these inkjet recording apparatuses eject ink droplets through nozzles, the shape, precision, and other properties of the nozzles have a significant effect on the ink droplet ejecting characteristics. The ink droplet ejecting characteristics are also affected by the surface properties of the nozzle forming member in which the nozzle holes are formed. It is known that, for example, uneven buildup of ink on the surface of the nozzle forming member around the nozzle holes would bend the trajectory of flying droplets, produce droplets of different sizes, cause fluctuations in the droplet flying speed, or cause other problems.
Several attempts have been made to solve these problems. For example, a method of forming a nozzle hole that prevents variations in the ink droplet flying direction is disclosed. The disclosed method includes the steps of attaching an adhesive member to one face of a nozzle forming member, applying a laser beam to the nozzle forming member from the other face in such a way that a part of the nozzle forming member remains after machining, and peeling off the adhesive member. Since the remaining part of the nozzle forming member is removed with the adhesive member, unmachined parts do not remain on the exit side of the nozzle hole.
As another attempt, a method of forming a nozzle by coating one face of a nozzle forming member with a fluorine-based polymer layer, forming nozzle holes by applying an excimer laser to the nozzle forming member from the other face, and removing the coating layer on the nozzle holes is disclosed. Further, as another attempt, a technique for stabilizing the flying of ink droplets is disclosed. This head is produced by forming on one face of the nozzle forming member a water-repellent film made of an organic resin layer containing a tetrafluoroethylene-based copolymer to provide a uniform surface on the nozzle forming member.
If a resin material is used as the nozzle forming member, it is difficult to form a water-repellent film on the surface of the resin material as described above, because the water-repellent agent has poor adhesion to the resin material. Several attempts to enhance adhesion of the water-repellent agent have been made, for example, by roughening the surface of the resin material to form microscopic asperities, but sufficient adhesion has not yet been achieved. The applied water-repellent agent initially provides good water-repellency, but its function gradually degrades because the water-repellent layer, if not adhered well, gradually peels off due to performance of repetitive wiping operations for removing ink droplets and foreign particles adhered to the nozzle plate and openings.
If a fluorine-based water-repellent agent is used, a silicon dioxide (SiO2) film is formed on the surface of the nozzle forming member formed of resin or another material in order to enhance the adhesion of the fluorine-based water-repellent. In this case, the SiO2 film should be sufficiently thick, 200 Å or more for example, to achieve sufficient adhesion. If excimer laser machining or the like is used to form nozzle holes, a suitable resin material such as polyimide should be selected for the nozzle forming member. The SiO2 film cannot be machined well and abnormal nozzle holes will be formed.
In the known nozzle manufacturing methods, the nozzle forming member and the liquid chamber forming member are cut into chips (i.e., individual heads) before being bonded to each other. After being cut into chips, the nozzle forming member and the liquid chamber forming member should be handled in chip units at the following stages. This requires a lengthy handling time at the bonding, excimer laser machining, and cleaning stages, resulting in low productivity in a mass production environment.
To address these problems, a recording head manufacturing method is disclosed. This head includes a nozzle substrate with a plurality of nozzles and a plurality of ink liquid chambers in communication with the nozzles. Actuators associated with the nozzles are driven to generate energy to eject ink droplets through the nozzles. In this recording head manufacturing method, the nozzle substrate is formed of a nozzle forming member and a liquid chamber forming member. The nozzle forming member has a water-repellent film on the ink-ejecting surface. The liquid chamber forming member partially forms the surface of the ink chambers and is bonded to the nozzle forming member, on the surface opposite the ink-ejecting surface.
When the liquid chamber forming member is bonded to the nozzle forming member, a liquid chamber forming member wafer that is integrally arranged of a plurality of liquid chamber forming members is bonded to the nozzle forming member to form a nozzle substrate cluster. Then, nozzles are formed in the nozzle forming member and the nozzle substrate cluster is cut into chips of a predetermined size, and individual chips are bonded to the actuators.
This cutting operation is performed by dicing as in known IC manufacturing. More specifically, a wafer that has been machined by an excimer laser is placed on the dicing machine with the UV-curable adhesive tape facing the machining table and diced along the chip contour of the liquid chamber forming member to produce individual nozzle substrates. This dicing operation is performed until the nozzle substrate cluster is completely cut and the UV-curable adhesive tape is cut halfway therethrough, i.e., into approximately half the thickness of the tape. This UV-curable adhesive tape can easily be expanded at the next stage. The dicing machine has also a cleaning station to remove sawdust immediately after dicing.
The cleaning operation performed in the above cleaning station, however, cannot completely remove the sawdust produced by dicing, because one face of the liquid chamber forming member having an intricate structure is blocked by the nozzle substrate and sawdust penetrates deep into the liquid chamber grooves. Accordingly, some dust may remain in nozzle holes and liquid chambers. As with the uneven buildup of ink, such remaining sawdust would bend the flying trajectory of ink droplets, produce ink droplets of different sizes, make the flying speed of the ink droplets unstable, or cause other problems.
As described above, the known droplet-ejecting heads formed by successively bonding a nozzle forming member with many nozzle holes, a liquid chamber forming member with liquid chambers corresponding to the nozzle holes, and an actuator substrate are manufactured by cutting a large wafer-like base material into chips and adhesive-bonding the chip-sized nozzle forming members and liquid chamber forming members thus obtained. Since the chips are cleaned before being bonded, it is relatively easy to remove dicing sawdust and foreign particles.
This known manufacturing method has a disadvantage, however, that positioning, bonding, and other operations are complicated because it is required to bond together small chips. Recently, to solve such problems, a new technique is being adopted, in which a sheet-like nozzle forming member cluster integrating a plurality of nozzle forming members is directly bonded to a sheet-like liquid chamber forming member cluster integrating a plurality of liquid chamber forming members, nozzle holes are then formed in the nozzle forming member cluster, and the bonded clusters are cut and separated into chips.
If this manufacturing method is adopted, another problem arises that it is difficult to remove the sawdust and other foreign particles that are produced in the cutting operation because they enter the nozzle holes and liquid chambers. As described above, it is difficult to completely remove sawdust and other foreign particles by cleaning using running water because the known inkjet recording heads (droplet-ejecting heads) have complicated grooves formed inside the clusters and have nozzle plates that are formed in the deep recess and have fine nozzle holes. If any sawdust or foreign particles remain, the ink ejection characteristics of the nozzles would be affected and defective heads would be produced.